TIDA-00176: Questions about encoder equations

Hello Wayne,

thank you for your feedback. The 'x' is a typo in equation 5 and should removed. Thanks for finding that.

The denominator N (line count) at the beginning of equation 5 is based assuming an integer number for 'incr' and used like with C code (int) on e.g. C2000 MCU. Since 'incr' is treated an integer number, shifting right removes the last two LSB, and the fractional part is removed (truncated). To make it more clear, I should have added this information to the equation 5.

The incremental count I use is 4-times the line count, but I ignore (truncate) the 4 quadrants (equivalent to 360 degree phase within one line count), by shifting two bits to the right. Then I take the angle derived from the arc tangent, which calculates the phase over one line count. This give the fractional part of the angle scaled to 360 degree. Please see figure 3 for illustration too.

Example:
Encoder line count 'N'[: 360
Incremental count 'incr', e.g. (360 x 4)-1 = 1439 (maximum incremental count before is rolls over to 0)
Incremental Phase 'phi', e.g.: 300 degree

360/360 x ((int) (1439 >> 2) + 300/360) = (359 + 300/360) = 359.83degree

Regards,
Martin